I think the primary way Mark deals with pain is by painting a picture of the passion of Christ. His main point is that there is one who experienced pain, so that we would not have to in the end. In other words, Jesus experiences death and suffering and defeats it on the cross and the resurrection. In this way, through faith in him, the followers of Jesus can live forever in beatitude and peace. Mark at one point says that Jesus came not to be served, but to serve and give his life as a ransom for many. The other gospels have a similar theology as well.